Industries, particularly, the food, cosmetic and pharmaceutical industries, need to evolve technologically in order to meet new consumer demands. Nanotechnology can provide interesting solutions for said industries.
In particular, nanotechnology has a great potential for revolutionizing the food, cosmetic and pharmaceutical industries, since it allows encapsulating biologically active compounds [BACs], e.g., essential oils, antioxidants, minerals, prebiotics, flavors, vitamins, etc., for the purpose of obtaining various benefits, for example, increasing the useful life of the product, reducing the amount of BACs to be used, controlling the release thereof, increasing the bioavailability thereof, masking unwanted tastes, etc.
Antioxidants, substances which are capable of generating a benefit for the health of the consumer, form a group of BACs the use of which arouses an increasingly greater interest. The encapsulation of said antioxidant compounds, e.g., quercetin or resveratrol, in particular systems (e.g., microparticles or nanoparticles), for the purpose of protecting them and keeping them stable during their storage, is a very interesting option.
To date, the application of encapsulated antioxidant compounds is generally limited to the cosmetic and pharmaceutical fields. By way of illustration, the encapsulation of quercetin in (i) nanocapsules formed by poly-lactic-co-glycolic acid (PLGA) and ethyl acetate (Ghosh et al., Life Sciences 2009; 84:75-80), (ii) nanoparticles formed by Eudragit® [poly(meth)acrylates] and polyvinyl alcohol (Wu et al., Int J of Pharm 2008; 346:160-168), and (iii) in lipid microparticles formed with phosphatidylcholine and tristearin (Sccalia and Mezzena, J Pharm Biomed Anal 2009; 49:90-94) has been described. Likewise, the encapsulation of resveratrol in (i) polycaprolactone nanoparticles (Lu et al., Int J of Pharm 2009; 375:89-96), (ii) pectin microparticles (Das and Ng, Int J of Pharm 2010; 385:20-28), (iii) liposomes (Caddeo et al., Int J of Pharm 2008; 363:183-191), (iv) chitosan microspheres (Peng et al., Food Chem 2010; 121(1):23-28) and (v) polystyrene microspheres (Nam et al., Polymer 2005; 46:8956-8963) has been described.
However, the application of encapsulated antioxidant compounds in the food field is very limited since the materials used to encapsulate said compounds have toxicity problems or are not approved for use in foods. Likewise, the use of antioxidant compounds in the design of functional foods is very limited due to, among other reasons, their short half-life, high liability and low oral bioavailability. The encapsulation of antioxidant compounds, such as quercetin or resveratrol, to protect them in the food and to keep them stable during their entire storage period, furthermore allowing a controlled release which increases their bioavailability in the organism would be very desirable.
As is known, when designing a carrier suitable for encapsulating a BAC it is very important to correctly select the material used as the coating agent of matrix; to that end, the dosage form, its toxicity, the product in which the formulation is to be incorporated, etc., must be taken into account among other factors.
In the food nanotechnology field, it is not recommendable to use synthetic polymers since they can have toxicity problems. Although natural polymers do not have those drawbacks, their use requires developing more complicated methods for producing particles and, furthermore, in most cases, the particle size obtained (usually greater than 100 μm) is difficult to control, therefore such microparticles can be perceived by the consumer and alter the organoleptic characteristics of the target food.
The use of proteins, both of an animal origin, e.g., casein, albumin, etc., and of a plant origin, e.g., prolamines, etc. (ES 2269715, US 2004/86595, U.S. Pat. No. 5,679,377), as BAC coating agents, has been described.
Zein is the main storage protein present in the corn grain seed. It is a globular protein belonging to the prolamine group since it tends to have a large number of proline and glutamine amino acids and is characterized by its high insolubility in water. In recent years, this protein has become very important in the scientific and industrial field due to its particular physicochemical properties and to its molecular structure since it has amphiphilic characteristics and can form different self-assembled structures according to the hydrophilic-lipophilic compounds present in the medium (Wang et al., Food Biophysics 2008; 3:174-181). Therefore, zein offers a number of potential advantages as a raw material of films, since it is capable of forming hard and hydrophobic coatings with excellent flexibility and compressibility characteristics which are furthermore resistant to microbial attack.
As a result of these properties, new applications have bee found for zein as a an adhesive, biodegradable plastic, chewing gum, coating for food products, fiber, cosmetic powders, microencapsulator for pesticides and inks, etc. (Muthuselvi and Dhathathreyan, Colloids and Surfaces B: Biointerfaces 2006; 51:39-43). This protein is also used by the pharmaceutical industry to coat capsules for the purpose of protecting, releasing in a controlled manner and masking unwanted tastes and aromas (Shukla and Cheryan, Industrial Crops and Products 2001; 13:171-192). Furthermore, it has been proposed for the microencapsulation of insulin, heparin, ivermectin and gitoxin. Stable microparticles/microspheres, even in high humidity and heat conditions, which are furthermore resistant to bacterial attack are generally achieved (U.S. Pat. No. 5,679,377).
However, the use of zein as an encapsulating agent in the food field for the design of functional foods with encapsulated ingredients is still incipient. Obtaining zein nanoparticles for encapsulating essential oils using the phase separation technique (Parris et al., J Agric Food Chem 2005; 53:4788-4792), as well as the encapsulation of omega-3 fatty acids in said protein by applying the fluid bed technique to protect them from oxidation and to mask their negative organoleptic characteristics when they are introduced in the foods of interest (MX2008003213), have been described. Furthermore, the encapsulation of lycopene and the polyphenol epigallocatechin gallate (EGCG) in zein fibers by means of the electrospinning technique (Fernandez et al., Food Hydrocolloids 2009; 23:1427-1432 and Li et al. J Food Sci 2009; 74 (3):C233-C240 respectively), lysozyme by means of the SAS (supercritical anti-solvent) process (Zhong et al. Food Chemistry 2009; 115(2):697-700) and fish oil by means of the liquid-liquid dispersion method (Zhong et al., J Food Process Pres 2009; 33(2):255-270) has recently been achieved. These works described manufacturing techniques which are relatively complex and difficult to scale for their application in industry, or are exclusively limited to the encapsulation of lipophilic compounds and are not suitable for the encapsulation of hydrophilic compounds.
It is therefore necessary to develop versatile systems for the encapsulation of biologically active compounds which overcome all or part of the aforementioned drawbacks, which are suitable for carrying both water-soluble and fat-soluble compounds and, in particular, compounds the administration of which by other means entails difficulties, as is the case of antioxidant compounds. Additionally, it would also be highly desirable for said systems to be obtainable in a simple manner and to have a suitable stability during their storage and after their administration, which would facilitate their application in different technological sectors, e.g., the food, pharmaceutical and cosmetic sectors.